Process for forming images



3,183,088 PROCESS FOR FORMING IMAGES Heman Dowd Hunt, Eatontown, NJ., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. FiledSept. 12, 1961, Ser. No. 137,534 11 Claims. (Cl. 96-.-27)

radiation-sensitive element after image exposure but be'-- fore development.

In assignees US. application Ser. No. 61,840; Patent No. 3,033,678, May 8, 1962, and application Ser. No. 852,190, Patent No. 3,033,682, May 8, 1962, there are described light-developabledirect writing radiation-sensitive elements suitable for oscillographic recording and similar uses which do not require liquid processing. These eles ments comprise novel .silver halide emulsion layers containing anexcess of water-soluble halide in an amount sufficient to provide an excess of'halide ions over that necessary to precipitate all of the silver in the watersoluble silver salts as silver halide and a relatively large quantity of stannous salts based on the silver halide. These elements are quite sensitive in the blue and ultraviolet regions of the spectrum and they are exposed by either high'pressure, mercury arc lamps, xenon lamps or any other source which is rich in blue and ultraviolet energy.

According to assignees Hunt US. application Ser. No. 117,805, filed June 19, 1961, it has been found that'the elements described therein, and above,-- which contain either a relatively high quantity (0.5 to 120 mole percent) of stannous salts alone or a relatively high quantity of' the stannous salts in combination with 0.1 mole percent or more of plumbous salt can be optically sensitized to form novel photosensitive products. To be'able to optically sensitize silver halide grains in the presence of a relatively large quantity of stannous salts, e.g. of the order of mole percent based on silver halide, as taught in said application, is quite surprising considering the fact that the stannous salt is in operative association with the silver halide grains. The optically sensitized silver halide and emulsion layers of said application makes it possible to use various other'sources of exposing radiation such as zirconium and tungsten lamps with attendant advantages. I

The process of this invention comprises (a) exposing to image-forming radiation containing radiation in the region of normal sensitivity of a silver halide photographic emulsion and/or in the region of extended sensitivity con-- ferred by the presence of an optical sensitizing dye, a washed, light-sensitive colloid-silver halide emulsion layer having an average grain size of 0.1 to 10 microns containing (l) 0.5 to 120 mole percent of a water soluble stannous salt, (2) a sensitizing amount of an optical sensitizing dye taken from the group consisting of eyanine, pseudocyanine, .car'bocyani'n'e and merocyaninedyes capable of extending the sensitivity of a silver bromide emul-' sion from the normal blue region to at least one of the green, red and infrared regions of the spectrum, and having added thereto (3) at least one water-soluble halide taken from the group consisting of lithium, sodium, po-

United States Patent tassium, calcium, magnesium and ammonium chloride,

bromide and iodide in an amount sufficient to provide an excess of halide ions over that necessary initially to pre--' ing the latensified element by exposing it to actinic light (i.e., radiation containing wavelengths from 3000 to 5000 A.) having an intensity less than the exposing radiation (a) for a period of at least 1 second. At room temperature, usually about 30 seconds are required to give an adequate visible image whereas at temperatures of 200"-v 300" F. a period of 1 second gives an adequate visible image. In general, there should be at least a 10% excess of halide ions present. Any photographic silver halide emulsion layer or elements embodying such a layer disclosed in application Ser. No. 117,805 can be used in the process. of this invention. The exposure step (a) can be carried out for about 0.01 to about 10,000 microseconds.

In the examples which follow, the coated materials were tested by using a Mark HI, Edgerton, Germenshausen Grier, Inc. electronic flash sensitometer similar to that described by Wyckotf and Edgerton, Journal of the Society of Mot-ion Picture and Television Engineers, 66, 474 (1957). This instrument uses a xenon discharge tube as a source of radiation. The exposure time was 10- seconds. The radiation was modulated with a x/i step tablet of 21 steps in the density range of 0.05 to 3.05. The latent image formed was latensified by yellow light attained by a yellow Wratten No. -8 filter modulation of white -watt fluorescent lights at 5 0 foot-candles intensity for a period of 5 seconds. Photo-development was then accomplished by removing the yellow filter and exposing the latensified element to white light -for a period of several minutes to obtain maximum image density.

With this type of development, an image of much higher density in the toe region of the sensitometric H and D 1 curve is obtained than has heretofore been possible. The latensified images may also be liquid-developed, stabilized and fixed. The instant invention will be illustrated but is not intended to be limited to, the following detailed examples.

Example I and 30 mole percent excess bromide ions,-all based on.

the. silver halide,'was made and coated in the manner described in Example I of assignees Hunt U.S. application'Ser. No. 117,805, filed June 19, 1961. The finished photographic element was exposed in the sensitometer described above to a- 10 sec. flash of the'xenon lamp and then latensified by exposure for 5 seconds through a Wratten No. 8 (K 2) filter having good transmission from about 500 mu on into the infrared, to a 40-watt white fluorescent lamp at 50 foot-candles intensity. The filter was removed and the image was photodeveloped for 30 minutes under the above fluorescent lamp. v The element was also exposed to blue light by means of a Wratten No. 47 filter, to green light by means of a Wratten No. 61

- filter and to red light by means of a Wratten No. 29

pages 591, 71

filter. The results shown below are given as the number of steps made visible by the exposure through the step See: Mees, "The Theory of the Photographic Process,"

4. ubllshedb The Mnemllla N York [1946 p y 0, ew

W I 'B G R K-2 I D21 Fog A ;11 I 12 s s"+1I .51 .17 I34 It will be seen that the latensification exposure through the K-2 filter for five seconds added one full /2 density step to the white light exposure. In other words step 18 of the step wedge is made visible by the white light exposure with the latensification step.

Example II Example I was repeated except that the emulsion contained 100 milligrams of the optical sensitizing dye: 3,3- diethyl-9-methyl benzothiazole carbocyanine p-toluene sulfonate per mole of silver halide. All exposure conditions were carried out as described in Example I with the following results.

w n G a K 2 Di, Fog A T is 12 12 1 s"+1 .55 21 I .34

Example III Example. I was repeated except that the emulsion contained 100 milligrams of the optical sensitizing dye: 5,5-

dibromo-3,3-diethyl-9-methyl benzothiazole carbocyanine p-toluene sulfonate per mole of silver halide. All conditions of exposure were the the same as describedin Example I. The exposure results were as follows:

w I n G R' K-2 1) Fog A 17 I 12 9 9 s"+1 .51v .23 .28

Example IV Example I was repeated except that the emulsion contrimethyl-3,3'-diethyl benzothiazole carbocyanine iodide. All exposure conditions were the same as those described in Example I with the following results:

w I 13 I o I R to: D11 Fog A 17 I 13 I 11 I o 5"+2 .51 .19 .32

ExampleV Example I was repeated except that the emulsion contained 100 milligrams of the optical sensitizing dye: 5,5- diphenyl-9-methyl-3,3 diethyl benzoxazole carbocyanine iodide per mole of silver halide. All conditions of exposure were the same as described in Example I with the following results.

W B Fog tained 100 milligrams of the optical sensitizing dye: 5,5,9- I

, Example VI Example I .was repeated except that the emulsion contained I00 milligrams of the optical sensitizing dye: 5- n1cthyl-3,l'-diethyl-2,2'-selenopseudocyanine iodide per mole of silver halide. All conditions of exposure were the same as described in Example I with the following results.

W B G I R K-2 Du FOE A Example VII Example I was repeated except that the emulsion contained milligrams of the optical sensitizing dye: 5,5- dimethyl-3,3',9-triethyl benzothiazole carbocyanine iodide per mole of silver halide. All conditions of expo sure werethe same as described in Example I with the following results.

w n o a K 2 D11 .Fog A Example VIII" Example I was repeated except that the emulsion contained 100 milligrams of the optical dye: 5,5- dimethyl 9 -j phenyl 3,3 diethyl benzothiazole earbocyanineiodide per mole ofsilver halide. All conditions of exposure were the sameas described in Example I with the'following results.

W B' I G- R K-Z D21 I FOE. A is 12 I a s s"+1 .53 I .22 .31

Example IX Example I was repeated except that the emulsion contained 50'milligrams of the merocyanine opticalsensitizing dye: 3 ethyl 5 [1- ethyl 2(1) benzoxazolidene-isopropylidene] 2 thio 2,4 oxazoledione. All exposure conditions were the same as those described in Example I with the following results.

W B G R K-2 D21 Fog I A 17 7 5"+2 39 I 09 I 30 Example-3' Example I was repeatedexcept that'theemulsioncontained 100 milligrams of the optical-sensitizing dye: 3- I n butyl 5 (3' ethyl- 2 thiazolidene ethylidene) rhodanine. All condition of exposurewere the same as those described inExample-I withthe followingresults.

w I n o R 'x-z- D ra A 10 I 1o 9+3, 13a .24 .09 ExampIeXI A gelatino silver chlorobron'iide emulsion was made containing about 4 mole percent excess brorm'de ion and 100 milligrams of the optical sensitizing dye set forth in Example V. Potassium iodide in an' amount'of 0.5 mole was added together-with sufiicient thiourea to provide 1% based on the silver-halide. The exposure conditions were the same as thosein Example I with the following results. I

w I B I o -R K-2 1).. Fog In 16 I I 4 5-+I .40 .19 I21 Example XII Example XI was repeated except that one mole percent of plumbous nitrate had been incorporated into the emulsion. All exposure conditions were the same as in Example I with the following results.

w K Z D :1 02 A Example XIII Example XH was repeated except that mole percentwas exposed to a 10" second xenon dash in thefl sensitomete r behind a neutral density fllter ot 1.3 in place of the V2 step wedge. The exposed material was then exposed for 5 and 60 seconds through a Wratten No. 47 blue filter, a Wraten No. 58 green filter or a Wratten No. 25 red filter I to light of varying intensity as shown in the tables below.

The material was then photodeveloped by exposing to-a white fluorescent light of 40-foot candles intensity for minutes. The results were determined by reading the.

densities on a reflection densitometer. The difference between the densities under the white light column andthose.

under the various filters shows the improvement gained,

the Wratten No. 25 red filter which transmits very effi-' of stannous chloride was added in the manner described .in Example I and an excess. of 64 mole percent ofbromide ion was added. The exposure operations were the same as described, in Example I with the following results.

0 R'I K-2 I 1)..

Fog ,A

Example XIV Example I was repeated except that the emulsion contained 200. milligrams of the optical sensitizing dye disclosed there instead of 100 milligrams per mole of silver halide. All conditions of exposure were the same as described in that example with the following results.

WIB-IG R K2IDnIFog A 19 I I 15 5"+2 .45 I .19 I.26

ExampleXV An emulsion as described in Example I but containing 160 milligrams per mole of silver halide of the optical sensitizing dye described in Example II was tested to show the efiect of varying the time of latensification through the K-2 filter. The exposure and photodevelopment times and conditions remained the same as in Example I. The results are as follows:

It will be seen that after about 60 seconds the latensifying efiect begins to fall ofi' when the above intensity for intensification is .used.

I Example X VI The photographic element described in Example I ciently light above 6000 A.

Foot-candles of intensifying 'Latenslficatlon time-5 seconds light helm-nagging through I Fog White 'Blue Green Red .25 .32 .29 .32 .35 .20 .33 .32 .35 .37 .25 .35 ,a0 .32 .se

Lntenstficatlon time-60 seconds .21 .28 Q25 .29 .35 .25 .34 .29 .36 .39 .22 .N .27 .35 .25 .3 .3l .35 .40 .23 .32 .28 .32 .35

Other filters may be used for the latensifying'step such as any minus blue filter and those which are minus blue and transmit efiiciently, radiation in the region where the particular optical sensitizing dye confers the greatest amount of spectral response to the emulsion.

It will be seen that the process of the invention offers several advantages. By being able to latensify the latent images in the manner taught by the invention a much lower energy image exposure is possible or by thesame token, a much higher effective speed is obtainedfrom high intensity exposures. In the former case, one could for instance expose the elements to electroluminescent panels and then by the instant process produce a suitable image. In the latter case, say'for oscillographic use the writing speed can be increased by about 150%. In other words the density of the image normally obtainable without latensification can be increased or more.

I claim:

1. A process'which comprises (a) exposing to image-forming radiation containing radiation in at least one of the regions'of normal sensitivity of a silver halide photographic emulsion and of extended sensitivity conferred by the presence of an optical sensitizing dye, a washed, light-sensitive colloid-silver halide emulsion layer having, lightdevelopable, direct-writing characteristics and an average grain size of 0.1 to 10 microns containing infrared regions of the spectrum, and having I added thereto (3) at least one water-soluble halide taken from the group consisting of lithium, sodium, potas 7 sium, calcium, magnesium and ammonium chloride, bromide and iodide in an amount sufficient to provide an excess of halide ions over that necessary initially'to precipitate all of the silver as silver halide, v

(b) latensifying the element resulting from the image exposure of step (a) by irradiating said element for about 1 to about 60 seconds with light radiation in the region of greatest response in the region of extra sensitivity conferred to the silver halide emulsion by said dye, and

(c) photodeveloping the latensified element by exposing it to actinic radiation containing wavelengths from 3000 to 5000 A. having an intensity less than the exposing radiation (a) for a period of at least one second.

2. A process according to claim 1 wherein step (c) is carried out with radiation of 50 foot-candles at a temperature of 200-300 F.

3. A process according to claim 1 wherein the emulsion contains an orthochromatic sensitizing dye and light radiaalso contains plumbous nitrate in an amount of 0.1 to 4.0

tion in the green region of the spectrum is used in latensify.

emulsion mole percent.

11. A process according to claim 1 wherein the emulsion layer is on a paper support.

References Cited by the Examiner UNITED STATES PATENTS 2,843,490 7/58 Jones 96-108 3,033,678 5/62 Hunt 96-108 3,033,682 5/62 Hunt. 3,047,392 7/62 Scott 96-108 3,063,350 ll/62 Massena 96-27 3,102,810 9/63 Sprague et al 96-27 3,107,138 10/63 Massena 96-27 OTHER REFERENCES Sheppard: "The Optical sensitizing of Silver Halides by Colloidal Silver," Journal of the Franklin Institute, vol. 210, No. 5, November 1930, pp. 587-608.

. Clerc: Photography Theory and Practice, 2nd edition, published by Pitman and Sons, Ltd., 1937, pp. 346 and 347 relied on.

' NORMAN G. TORCHIN, Primary Examiner.

HAROLD H. BURSTEIN, Examiner. 

1. A PROCESS WHICH COMPRISES (A) EXPOSING TO IMAGE-FORMING RADIATION CONTAINING RADIATION IN AT LEAST ONE OF THE REGIONS OF NORMAL SENSITIVITY OF A SILVER HALIDE PHOTOGRAPHIC EMULSION AND OF EXTENDED SENSITIVITY CONFERRED BY THE PRESENCE OF AN OPTICAL SENSITIZING DYE, A WASHED, LIGHT-SENSITIVE COLLOID-SILVER HALIDE EMULSION LAYER HAVING LIGHTDEVELOPABLE, DIRECT-WRITING CHARACTERISTICS AND AN AVERAGE GRAIN SIZE OF 0.1 TO 10 MICRONS CONTAINING (1) 0.5 TO 120 MOLE PERCENT OF A WATER SOLUBLE STANNOUS SALT, (2) A SENSITIZING AMOUNT OF AN OPTICAL SENSITIZING DYE TAKEN FROM THE GROUP CONSISTING OF CYANINE, PESUDOCYANINE, CARBOCYANINE AND MEROCYANINE DYES CAPABLE OF EXTENDING THE SENSITIVITY OF A SILVER BROMIDE EMULSION FROM THE NORMAL BLUE REGION TO AT LEAST ONE OF THE GREEN, RED AND INFRARED REGIONS OF THE SPECTRUM, AND HAVING ADDED THERETO (3) AT LEAST ONE WATER-SOLUBLE HALIDE TAKEN FROM THE GROUP CONSISTING OF LITHIUM, SODIUM, POTASSIUM, CALCIUM, MAGNESIUM AND AMMONIUM CHLORIDE, BROMIDE AND IODIDE IN AN AMOUNT SUFFICIENT TO PROVIDE AN EXCESS OF HALIDE IONS OVER THAT NECESSARY INITALLY TO PRECIPITATE ALL OF THE SILVER AS SILVER HALIDE, (B) LATENSIFYING THE ELEMENT RESULTING FROM THE IMAGE EXPOSURE OF STEP (A) BY IRRADIATING SAID ELEMENT FOR ABOUT 1 TO ABOUT 60 SECONDS WITH LIGHT RADIATION IN THE REGION OF GREATEST RESPONSE IN THE REGION OF EXTRA SENSITIVITY CONFERRED TO THE SILVER HALIDE EMULSION BY SAID DYE, AND (C) PHOTODEVELOPING THE LATENSIFIED ELEMENT BY EXPOSING IT TO ACTINIC RADIATION CONTAINING WAVELENGTHS FROM 3000 TO 5000 A. HAVING AN INTENSITY LESS THAN THE EXPOSING RADIATION (A) FOR A PERIOD OF AT LEAST ONE SECOND. 